Temperature responsive control apparatus



A 1951 F. D. JOESTING 2,564,222

TEMPERATURE RESPONSIVE CONTROL APPARATUS Filed ,Nov. 5; 1947 I L g r l-J Zmnentor F/fEDE/i/C/f 0. J05TING (Ittorneg Patented Aug. 14, 1951TEMPERATURE RESPONSIVE CONTROL APPARATUS Frederick D. Joesting, OakPark, Ill., assignor to Minneapolis-Honeywell Regulator Company,Minneapolis, Minn., a corporation of Delaware Application November 3,1947, Serial No. 783,657

3 Claims.

The present invention relates to a bleed type pneumatic snap actingthermostat using a permanent magnet for the snap action.

Snap action pneumatic thermostats are especially desirable for controlapplications such as one pipe steam heating systems. In these systems,the steam valve must be either fully open or completely closed toexercise proper control and to minimize heating system noises, thisrequiring, in a bleed type pneumatic control system, snap acting controldevices. Various types of mechanical snap acting mechanisms have beenused in pneumatic thermostats but they have resulted in expensive andbulky constructions. Permanent magnets have long been used for snapaction in electric thermostats but, due to the peculiar requirements ofpneumatic control devices, they have not, prior to the present device,been successfully used in a pneumatic thermostat. It is thus a principalobject of this invention to provide an improved snap acting pneumaticcontrol device.

It is a more specific object to provide a simple and compact pneumaticthermostat using a permanent magnet for snap action.

It is also an object to provide a snap acting control device havingrelatively movable control members wherein one of the members isactuated through a strain release mechanism by an auxiliary leveroperated by a condition re-,

These and other objects will become apparent upon the study of thefollowing specification and drawings wherein:

Figure 1 is a left elevation view of the present thermostat with partsbrokenaway and other Figure 4 is a section view of certain operativeparts taken on the line 4-4 of Figure 2.

Figure 5 is a similar section view taken on the line 5-5 of Figure 2.

Referring to Figure 1, the present thermostat is shown complete with itscover In but without the subbase or mounting plate by which it isattached to a Wall or the like. Cover I0 is held in place by down-turnedtongues I l coperating with suitable notches at the top of base 18 andby a suitable clamp screw I3 at the bottom of the instrument. This coverand its attachment, as shown in Figure 1 and as above described, isconventional and forms no part of the present invention. Screws l4,accessible from the front of base l8, are used to attach the base to themounting plate or sub-base, not shown.

The control members or elements of the present device comprise a nozzle[5 and a movable valve plate l6, these members being carried by abracket member I! attached to base I8. Nozzle I5 extends outwardly atright angles to base l8 and is mounted in a connector block 19 securedto the back side of the outer portion or platform 20 of bracket ll. Atube 2| connects connector block I9 to a suitable fitting 22 which isused to connect the thermostat-to the branch line of a pneumatic controlsystem, not shown. When valve plate I 6 is in engagement with nozzle l5,no air can escape hence pressure may build up to a maximum in the branchline of the control system, whereas, when plate I6 is sufiicientlyremoved from nozzle l5, air in the branch line may bleed out through thenozzle l5 and thus reduce the branch line pressure in a manner common tobleed-type controllers.

Valve plate I6 is essentially triangular in shape and is pivotallymounted near its base on a pair of pedestal members 24 attached to theouter surface of platform 20, each of the members 24 having an outerpivot pin portion 25 with an inner shoulder 26 formed by an adjacentguide pin portion 21 of a diameter greater than 25. Holes 28 in plateI'B are of sufficient diameter to fit loosely over pin portions 25 buttoo small to slip over shoulders 26, one of the holes being elongatedalong the line defined by the holes to minimize assembly difficulties.

A compression spring 3| is adjustably held against plate l6 by a bolt 32located on the base side of the pivot axis and. opposite from the nozzleengaging portion of the plate, hence this spring biases plate I 6 aboutpins 25 and shoulders .26 in a manner to disengage said plate fromnozzle I5 and also holds the plate It in place on said pin portions andagainst said shoulders,

To provide a mechanism for actuating plate I6 against the bias of spring3 I, and the force due to air blowing through nozzle [5 against saidplate, a substantially T-shaped. auxiliary lever 34 is secured in spacedrelation to the inner side of plate l6 by a bolt 35 and a compressionspring 36, bolt 35 being screwed into lever 34 but engaging plate Itonly through spring 36 in a manner to urge lever 34 and plate l6together. Lever 34 is guided by holes 38 fitting over guide portions 21of pedestal members 24 and includes projections 40 formed in the upperportion of the lever 34 for engaging the base portion of member It tospace the upper portion of the lever from the base portion of plate I6and to act as pivot points. An adjustable stop screw 4| carried by plateIt and engageable by lever 34 limits the proximity of the lower end ofthe lever to member IS. The lever 34 also carries an adjustable stopscrew 42 that coacts with the outer surface of platform 20 to limit themovement of lever 34 toward that surface. An outwardly directed tipportion 43 formed at the lower most part of lever 34 is adapted to beengaged by a suitable condition responsive means, as will be seen.

The temperature sensitive element or condition responsive means, of thepresent thermostat comprises a generally U-shaped bimetal element 45attached to base I8 by a hinge 46, the element having its most expansivemetal on its outside so that it tends to contract with a rise intemperature. The inner arm 41 of the element 45 is somewhat longer thanouter arm 48 and its free end bears against a cam 49 operable by theadjusting dial l2. Rotation of cam 49 by dial l2 shifts the position ofthe bimetal 45 and thus changes the control point of the instrument. Aspring 5| is arranged between the lower end of element 45 and the baseI8 to bias the element in a counterclockwise direction (Figure l) andthus normally maintains the free end of arm 41 against cam 49. The otherfree end of the element 45, the upper end of arm 48, carries an abutmentplate 53 for engaging the pivot portion 43 of lever 34 upon atemperature rise. A magnet armature 54 is attached to the underside ofarm 48 by the same screws that hold plate 53 and cooperates with asmall, notched, permanent magnet 55 held by a clamping arm 56 fittingwithin the notch and coacting with an angular support member 51 attachedto the underside of platform member 20.

Armature 54 is so positioned relative to bimetal arm 48 and stop 42 isadjusted in such a manner that the armature 54 and magnet 55 areslightly spaced when arm 34 is urged to its innermost position byabutment member 53. At this point, the attraction of magnet 55 forarmature 54 is at its maximum effectiveness, its attractive force atthis point being suflicient to deflect the bimetal element 45 to someextent and to overcome springs 3| and 35 and the force on member I5 dueto the air pressure in nozzle |5.

To better illustrate the relative strength of the aforementioned springsand the magnet, as well as to show the function of the apparatus,

.its operation is explained below.

Operation An inspection of the drawing shows member IS in engagementwith nozzle I5, lever 34 is spaced a short distance below stop screw 4!,and stop screw 42 is in engagement with platform 20, lever 34 being heldin this lower most position due to a contraction of the bimetal element45 and inward movement of arm 48 brought about by a relatively hightemperature affecting said element and by the attractive force of magnet55.

If the temperature should now decrease, arm 48 tends to move outward dueto the action of the bimetal element 45 and spring 36 but it isrestrained by the force of magnet 55 acting on armature 54, thus storingresilience in element 45. However, upon a continued decrease intemalumna-mm:

4 I perature, the expansive force of the bimetal increases and becomessufficient to move armature 54 slightly further away from its positionnear magnet 55, this movement permitting a like movement of lever 34 buthaving no effect on valve member l6 until the movement becomessufiicient for lever 34 to engage stop screw 4|. Because the initialmovement of arm 43 does not affect valve member l5 and as it is held inengagement with nozzle |5 by the force of spring 33, there is no leakageat the nozzle which could interfere with the proper operation of thecontrol device.

While arm 48 moves slightly outwardly, however, the attractive force ofthe magnet 55 on armature 54 diminishes very rapidly. The lessenedmagnetic force permits the resilience stored in bimetal element 45 tofurther increase the outward movement of arm 48 and still further reducethe magnetic attraction, resulting in a rapid or snap movement of arm 48by the time lever 34 engages stop pin 4|. An abutment plate 53 on arm 48tends to disengage tip 43 of lever 34, spring 3|, assisted by the airpressure of noz- Zle I5, is effective to bias member I5 away from nozzlel5 and full open the valve, a considerable movement being possiblebecause of the resilience in element 45 causing additional movementoutwardly of arm 48 as the restraining forces are minimized.

With the thermostat valve fully opened, as above described, an increasein temperature will cause a contraction of bimetal 45 and tend to movearm 48 inwardly but, upon plate 53 engaging tip 43 of lever 34, theresistance to further movement of plate I6 and lever 34 caused by spring3| will cause some resilience to be stored in the bimetal element. Asthe temperature continues to decrease, however, the contracting force ofthe element 45 is sufficient to start moving lever 34 and plate Ittoward closed position, plate I6 following lever 34 because spring 36 iseiiectively stronger than spring 3|. As this movement takes place,armature 54 is being moved toward magnet 55 and the attractive force ofthe magnet for the armature increases rapidly. With the contractingforce of the bimetal substantially balancing the resisting force ofspring 3| and the air pressure from the nozzle I5, only a slightincrease in themagnetic attraction is sufficient to cause furthercontractive movement of the bimetal which still further increases themagnetic attraction with the result that the member l6 and lever 34 aresuddenly moved to their innermost positions. On this occurring, memberl6 engages and closes nozzle l5 but a further slight movement of lever34 is permitted by strain release spring 36, this spring limiting theclosing force that can be imposed on member I6 and permitting movementof lever 34 without an accompanying movement of member I6, as beforedescribed. Obviously, member I6 is held against nozzle 5 by the force ofspring 36 whenever lever 34 is out of engagement with stop screw 4|,thus preventing air leakage from the nozzle.

Because the above described mechanism is such that valve member I3 iseither in engagement with nozzle I5 or spaced an appreciable distancetherefrom, and as both the closing and opening movements of the valvemember are accomplished with great rapidity, the present device is aneffective two position snap acting pneumatic thermostat.

While the above description has been in terms of a thermostat, obviouslyany control device having a resilient actuating element may besubstituted for the bimetal described. As this and other substitutionsare readily apparent to those skilled in the art, the scope of thepresent invention is to be determined only by the appended claims.

I claim as my invention:

1. A fluid control device comprising valve members relatively movable toopen or closed positions, means for definitely guiding one of saidmembers relative to the other, a lever means for moving said one valvemember in one direction, spring means for moving said one member in anopposite direction, means for resiliently attaching said lever means tosaid one member so that said lever means is carried by said one member,stop means coacting with said lever means for limiting the movement ofsaid lever means in a direction to close said. valve, raid limitingmeans permitting a predetermined movement of said lever means after saidvalve is in a closed position resulting in a stressing of said resilientattaching means, a condition responsive means for mov-' me said levermeans and the attached valve member against said spring means, anarmature attached to said condition responsive means, and a permanentmagnet for attracting said armature.

2. A control device comprising a base and having relatively movablecontrol members mounted thereon, a movable lever member, resilient meansfor urging one of said members and said lever means together, springmeans for biasing said one member in one direction, said one directionbeing opposite to that of the bias of said resilient means, said springmeans having less ability for controlling motion of said one member thanhas said resilient means, condition responsive means attached to saidbase and engageable with said lever means in a manner to move said onemember against said biasing spring, and permanent magnet meanscooperating with said resilient means and said spring means for causingsaid one member to assume one of two predetermined positions when saidlever means is actuated by said condition responsive means.

3. A control device comprising a base and having relatively movablecontrol members mounted thereon, a movable lever attached to one of saidmembers in pivotal relation thereto, resilient means for urging said onemember and said lever means together, spring means for biasing said onemember in one direction, said one direction being opposite that of saidurging means, said spring means having less ability for causing motionof said one member than has said resilient means, condition responsivemeans adjustably mounted on said base and engageable with said levermeans in a manner to move said one member against said biasin spring,and permanent magnet means arranged to oppose said biasing means with amaximum force when said one member is in one of two positions and tooppose said biasing means with considerably reduced force when said onemember is in the other of the two positions.

FREDERICK D. J OESTING.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,286,012 Jarvis Nov. 26, 19181,412,773 Colgate Apr. 11, 1922 1,606,355 Fisher Nov. 9, 1926 1,724,347Fortier Aug. 13, 1929 1,901,754 Leake Mar. 14, 1933 1,983,821Snediker 1. Dec. 11, 1934 2,096,502 Wetzel Oct. 19, 1937 2,298,827Joesting Oct. 13, 1942 FOREIGN PATENTS Number Country Date 291,923 GreatBritain June 14, 1928

